Respiratory virus shedding in exhaled breath and efficacy of face masks

Nature/Science level of evidence when you're talking about a relatively low-risk intervention like wearing a bandana. In the words of the author of one the studies you disdain: "In normal times we'd say that if it wasn't shown statistically significant or the effective in real-world studies, we don't recommend it," he said. "But in the middle of a pandemic, we're desperate. The thinking is that even if it cuts down transmission a little bit, it's worth trying." BTW, the author of the study I'm talking about here studied transmission of viral infections (influenza and coronaviruses) with an n of 111, not bacterial infections: https://www.nature.com/articles/s41591-020-0843-2 But there are multiple studies from the past decade that indicate that masks help prevent spread of respiratory viruses. Finally, you harshly criticize my comment for lack of evidence, and yet you pull this one out: "It's likely that in members of the public the main route is touching an infected surface and then touching your eyes, nose or mouth." We have no idea if that's true or not at this point. And here's another statement you pulled out of nowhere: "As soon as you drop any of those you're not just making the mask a bit less effective, you're probably increasing the risk over not wearing a mask at all." You seem to have started from a position of defending the CDC, and then from there gone on cherry pick evidence or pull statements out of thin air. There are people I know working at the CDC that I respect a great deal. But this PR campaign to lie to the American people to preserve mask stocks was a bad, bad idea. > We know that qualified registered healthcare professionals who know the consequences of not wearing PPE correctly still struggle to do it all correctly. No significant difference between fitted and non-fitted N-95 masks: https://www.ncbi.nlm.nih.gov/pubmed/21477136 And no, I wasn't even talking about wearing hospital-level PPE. I was talking about masks, and even mentioned bandanas, for crying out loud. But keep on spearing that red herring. And here yet again, obviously N95 masks can help prevent transmission of respiratory viruses, including SARS-CoV-19. We know this to be true. > This is not the CDC / WHO / etc lying, this is them talking about the science as they understand it. You linked to some random ICU nurse, who makes some great points but has nothing to do with the CDC or WHO. But I agree that frontline health workers should absolutely have precedence to N-95 masks and other PPE. > You're basing this on a small study carried out in a lab using research bacteria (not viruses) carried in a calibrated spray, that didn't include "people breathing through the mask". Finally, you have no idea what I'm basing this on. Actually, it's common sense here that if you're infected, even as an asymptomatic carrier, wearing a bandana can reduce spread of droplets.

sake of easy numbers, let's assume that wearing a mask captures 90% of infectious droplets and that every meter of distance results in 60% of the droplets in the air to fall to the ground. If a sick individual wearing a mask coughs out 100 starting droplets and is 2 meters away from a healthy individual, the healthy individual will be breathing in 2.5 infectious droplets (100 * 0.10 * 0.50^2). This is multiplicative. For what it's worth, in real-world studies, when the use of face masks and/or social distancing became enforced, the rate at which infectious transmission occurred saw a measurable drop. The introduction of mandates requiring face masks (with social distancing already in effect) saw a 2% decline in the daily growth rate of COVID (3). If you'd like to read more, there is a recent meta-paper that surveys 172 different studies and concludes that: "The findings of this systematic review of 172 studies (44 comparative studies; n=25 697 patients) on COVID-19, SARS, and MERS provide the best available evidence that current policies of at least 1 m physical distancing are associated with a large reduction in infection, and distances of 2 m might be more effective. These data also suggest that wearing face masks protects people (both health-care workers and the general public) against infection by these coronaviruses, and that eye protection could confer additional benefit. However, none of these interventions afforded complete protection from infection, and their optimum role might need risk assessment and several contextual considerations. No randomised trials were identified for these interventions in COVID-19, SARS, or MERS." (4) 1: https://www.nature.com/articles/s41591-020-0843-2 2: https://www.thelancet.com/journals/laninf/article/PIIS1473-3... 3: https://www.healthaffairs.org/doi/10.1377/hlthaff.2020.00818 4: https://www.thelancet.com/journals/lancet/article/PIIS0140-6...

masks. Research like the paper I mentioned above, as well as the realization that asymptomatic and presymptomatic people play a large role in spreading the virus convinced the scientific community that widespread wearing of surgical masks is helpful. But blaming institutions for not knowing the right answer early on seems very unfair to me. 1. https://www.nature.com/articles/s41591-020-0843-2

and/or, "The Most Uncomfortable Thing I've Ever Done". I have awful seasonal allergies and asthma and when I'm at the office or out and about in public, I will wear my surgical mask the entire time. The only time my mask is off is when I'm in my car or at home. I just can't get past the entitlement that some people have when they can't be bothered with sacrificing a tiny little bit of personal comfort to help slow the spread of a pandemic. 1: https://www.nature.com/articles/s41591-020-0843-2 2: https://health.clevelandclinic.org/heres-how-wearing-a-cloth... 3: https://www.mayoclinic.org/diseases-conditions/coronavirus/i... /rantover I apologize, but I'm just shocked. I expect better from my fellow HNers. Also, It's not entirely clear to me if you don't believe in wearing masks or if you're just making the comment that a mask is a political object (and by extension, websites should not display politically charged images). Either way, your comments in this thread have really thrown me for a loop.